ChartGridPreset:
    | "1x1"
    | "1x2"
    | "1x3"
    | "2x1"
    | "3x1"
    | "2x2"
    | "1x4"
    | "4x1"
    | "2x3"
    | "3x2"
    | "2x4"
    | "4x2"
    | "3x3"
    | "3x4"
    | "4x3"
    | "4x4"

The uniform layouts, rows by columns: every chart one cell, no spans. The first six are the ones 2.5.9 shipped.